Radio networks according to the P25 technological standards are widespread throughout the world, with a high concentration in the American continent; they are used in a professional context, in particular for the needs of public security forces. These networks use reserved narrow frequency bands, with channels of width 12.5 kHz (P25 Phase 1—FDMA) or 6.25 Khz (P25 Phase 2—TDMA or FDMA), spaced apart by 6.25 kHz. These networks offer a very complete set of functions not necessitating a high data rate. The networks are constituted by radio sites the range of which is relatively long.
Conversely, radio networks of the fourth generation or later, principally based on the Advanced 3GPP LTE technology, use radio sites of often shorter range on different frequency bands, used with very wide channels offering services necessitating high data rates.
Linking these two types of networks is of great interest.
It has in particular been envisaged to develop radio terminals capable of transmitting and receiving in both modes (P25 and LTE) configured for using the LTE networks where they are covered by the latter and the P32 networks in the opposite case. This method of linking the two types of networks does however have numerous drawbacks. In particular, this solution necessitates the complete changing of all the terminals in service as well as the installation of high level service gateways.
It has moreover been envisaged to use 3GPP LTE networks as a transport layer for the 25 networks: this method also has many drawbacks. In particular, it does not allow direct linking between LTE radio terminals and P25 radio terminals.
Finally, gateways between a P25 network and an EPS network with LTE radio access are known. These gateways provide simple network interlink functions, without being able to provide real integration. For example, mobility is not managed and a calling terminal must dial the number of a correspondent according to the place where the latter is assumed to be.